The bot replies with a message in private with a string like this:
- You must calculate the square root of the number n°1 and multiply the result by the number n°2.
- Then you need to round to two decimals.
Statically calling a non-static method from another class.
Abusing a language flaw that was only valid in PHP versions 5.0.0 to 5.1.2, see http://3v4l.org/mAPH4.
Making the called method static won't work, see http://ideone.com/expLQq, the only viable solution seems to be using traits to clear this mess up: http://ideone.com/QABR3b
This would require PHP 5.4 or higher to be used, which you should be doing anyway...